Trigger points might be "active" or "latent." An active trigger point is painful even when no pressure is applied to it, and the pain may limit the use of the muscle, leading to weakness and decreased range of motion. A latent trigger point does not cause pain during daily activities, but it will feel sore when pressure is applied to it, and may become activated if the muscle is injured.
Doctors aren't sure what causes trigger points. They may result from a single serious injury to a muscle or from repetitive minor injuries to a muscle area. Other possible causes of trigger points include poor posture, a vitamin deficiency, joint problems or maintaining an awkward body position. Trigger points are also common symptoms in people who have a condition called chronic myofascial pain (CMP), a neuromuscular disorder that affects the muscles and the tissue surrounding them (fascia).
Exercise, stress relief and over-the-counter medications like ibuprofen or acetaminophen can help relieve pain and inflammation from trigger points. If those measures don't work, a doctor can sometimes inject a pain reliever, a water solution or a corticosteroid directly into the trigger point. Botulinum toxin is also sometimes used for trigger point injections. Sometimes simply inserting a needle into a trigger point without injecting medicine into it can break the pain cycle and bring relief.